Triton is one of the few satellites in the Solar System which shows an ongoing geological activity, with plumes and geysers whose origin is still controversial . Its surface is relatively young, as shown by the paucity of craters detected on its surface . Our knowledge of this moon comes from the Voyager 2 mission, which obtained several images, covering about 40% of Triton’s surface . However, few studies were focused principally on surficial geomorphology, and those are mostly limited to the cantaloupe region and surrounding areas. Triton’s crust is composed predominantly by solid nitrogen (N2) but several other ices have been detected . Crater counting has revealed that the surface is very young and likely it went through a resurfacing process in the past. In fact, a very small number of craters has been detected, and these usually exhibit a typical bowl-like shape . Geological features on Triton include regions, called terrains, such as cantaloupe terrains or plains, which show different textures. Usually, plains are categorized within smooth, walled and terraced plains . The latter are the flattest areas on Triton, a characteristic which has been explained by evoking a lava-like or other viscous liquid infill. Their central depressions also present a cluster of irregular pits, which have been interpreted as drainage pits or eruptive vents . These peculiar morphologies seem to indicate the presence of a viscous fluid on the surface in a remote epoch, which may imply potential climatic and atmospheric changes during Triton’s geological history. In this work we analyse an area located at NW of Tuonela Planitia, which shows several depressions rimmed by sharp margins. Two of these depressions are named Kulilu Cavus and Mah Cavus . Cavi are elliptical-shaped depressions, distributed in an ordered trend, which constitute the cantaloupe terrain . Diapirism is the main candidate process to explain these collapsed depressions  but other hypotheses, such as cryovolcanism or impact cratering , have also been proposed. Methodology A new geological map has been realized. We used Voyager 2 imagery named c1139533  (600 m/px), properly calibrated, filtered and georeferenced using the Integrated Software for Imagers and Spectrometers (ISIS4) . We mapped the different geological units and main features according to differences in surface morphology (fig.1). We also produced a DEM of the study area, using the open-source suite of tools NASA Ames Stereo Pipeline (ASP) . We applied the photoclinometry-based “shape-from-shading” (SfS) tool to produce the DEM. Since SfS needs an input DEM generated preferably with stereo images, and we do not have such data for Triton, we used the methodology proposed by Lesage et al. 2021. We analysed four different cross sections to measure the relative height of Kulilu Cavus, Mah Cavus and two other depressions, as well as their associated terraces (fig.2). Discussion Geologic
We present our latest understanding of the processes that shape the spatial distributions of energetic electrons trapped in the magnetospheres of Uranus (L < 15) and Neptune (L < 25). To determine what controls the energy and spatial distributions throughout the different magnetospheres, we compute the time evolution of particle distributions with the help of a diffusion theory particle transport code that solves the governing 3-D Fokker-Planck equation. Different mechanisms of particle loss, source and transport are numerically examined. Our theoretical modeling is guided by the analysis of particle, field and wave data collected during Voyager 2’s flyby of Uranus in January 1986 and at Neptune in August 1989. Our preliminary data-model comparison results at Uranus show that adiabatic transport cannot explain the radial and angular features of warm to ultra-relativistic electron populations within the ~1-15 L region. Our simulation results also suggest that, with absence of loss mechanisms inside L = 15, energetic and radiation-belt electron populations would be higher by 1-3 orders of magnitude in intensity close to the planet (L ~ 1-8). Particularly, our results confirm that moon sweeping effect is a significant loss mechanism at Uranus. Nonetheless, other radial, energy and pitch-angle dependent mechanisms seem to be missing to explain the in-situ data. We will thus present our ongoing effort to examine the role of - for instance, Uranus’ rings system, atomic hydrogen corona and wave activity inward of L ~ 8-10 to improve our modeling of Uranus’ electron populations between L values of 1 and 15. Our first physics-based model of energetic electrons at Neptune will be presented, emphasizing first the role of radial transport and moon sweeping effect for the 1-25 L region before investigating new processes. Our models developed for Uranus and Neptune are based on the theoretical modeling of electron distributions at Saturn, which included the modeling of radial transport and interactions of electrons with Saturn’s dust/neutral/plasma environments and waves, as well as particle sources from high-latitudes, interchange injections, and outer magnetospheric region. Comparisons between the distributions of electron populations at Gas and Ice Giant systems will be discussed. Data analysis, theoretical modeling, and numerical computations for Uranus and Neptune are carried out by adapting the Kronian modeling tools developed at Southwest Research Institute to the Ice Giants environment. Key data analysis, theoretical modeling, and numerical computational tasks for Saturn were carried out at Southwest Research Institute under NASA GSFC grant 80NSSC18K1100.